/*
 * Copyright (C) 2018 bzt (bztsrc@github)
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy,
 * modify, merge, publish, distribute, sublicense, and/or sell copies
 * of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 */

#include "delay.h"

/**
 * Wait N CPU cycles (ARM CPU only)
 */
void wait_cycles(unsigned int n)
{
        if (n)
                while (n--)
                {
                        asm volatile("nop");
                }
}

/**
 * Wait N microsec (ARM CPU only)
 */
void wait_msec(unsigned int n)
{
        register unsigned long f, t, r;
        // get the current counter frequency
        asm volatile("mrs %0, cntfrq_el0"
                     : "=r"(f));
        // read the current counter
        asm volatile("mrs %0, cntpct_el0"
                     : "=r"(t));
        // calculate required count increase
        unsigned long i = ((f / 1000) * n) / 1000;
        // loop while counter increase is less than i
        do
        {
                asm volatile("mrs %0, cntpct_el0"
                             : "=r"(r));
        } while (r - t < i);
}

/**
 * Get System Timer's counter
 */
unsigned long get_system_timer()
{
        unsigned int h = -1, l;
        // we must read MMIO area as two separate 32 bit reads
        h = *SYSTMR_HI;
        l = *SYSTMR_LO;
        // we have to repeat it if high word changed during read
        if (h != *SYSTMR_HI)
        {
                h = *SYSTMR_HI;
                l = *SYSTMR_LO;
        }
        // compose long int value
        return ((unsigned long)h << 32) | l;
}

/**
 * Wait N microsec (with BCM System Timer)
 */
void wait_msec_st(unsigned int n)
{
        unsigned long t = get_system_timer();
        // we must check if it's non-zero, because qemu does not emulate
        // system timer, and returning constant zero would mean infinite loop
        if (t)
                while (get_system_timer() - t < n)
                        ;
}
